3 Answers
3

Remember that deleting still takes a certain # of votes, so when you vote to delete, it is an implicit flag (as Ólafur Waage mentioned) to other 10k users that they might want to vote to delete it too.

I would remind you that sometimes closed duplicates are useful to keep around for the reasons outlined in this blog post:

When you've just passed 10k, I suggest looking at the delete tab in the tools section. Check out what kind of questions have delete votes and what questions have just been deleted.

You can kinda get the feeling from it there. It's just something you learn, same with the close vote.

The questions that are deleted are usually nonsense and spam. But there are other things that are deleted, like questions that clearly don't belong here and anywhere else. Like how do you get a serial number for X.

I'm new to this too. My rule of thumb is that I only vote to delete anything that is 100% trash (spam, rants, etc). That's just my rule - it doesn't apply to everyone else. I'll let the more experienced users and mods delete other questions.